Low-charged battery compatible harmonic reflector integrated in a mobile device for detection of trapped victims

This paper presents a harmonic reflector integrated in a mobile device for detection of trapped victims. With no power consumption, the module consisting of an antenna and a schottky diode generates a second harmonic tone (2f₀) for an incident fundamental tone signal (f₀) and reflects it. Therefore, the reflected harmonic signal is a good candidate for an indicator of the location of trapped victims in post-disaster situations. The harmonic based module is successfully integrated in a commercial smart phone to show an application of the harmonic reflector to a mobile device. For effective isotropic radiated power (EIRP) of 30 dBm, the coverage of 30 m is measured in a noise level of -110 dBm with a dc voltage of 0.5 V applied to a schottky diode while the range is 5 m with an unbiased diode. This result implies the feasibility of the detection of victims using a second harmonic signal reradiated from their personal mobile devices even with a low charged battery.